1. Field of the Invention
The present invention relates to a derailleur, and more particularly, to a bicycle derailleur device that is compliant and self returning.
2. Prior Art
Because of the various meanings in English of the word xe2x80x9cderailleurxe2x80x9d it is considered necessary to clarify the manner in which this word is used in this specification. This particular word xe2x80x9cderailleurxe2x80x9d was apparently adopted into the English language from French in the mid 1800""s to designate a mechanism for removing a wheel from a rail or for removing several wheels from a set or pair of rails. As time has progressed, this term xe2x80x9cderailleurxe2x80x9d has been used in English to designate a mechanism for shifting a flexible belt, chain or the like from a first gear or similar member to an adjacent coaxial gear or similar member. The word xe2x80x9cderailleurxe2x80x9d is also utilized to designate the precise structure within such a mechanism which engages and physically re-positions such a belt, chain or the like.
Derailleur mechanisms have been commonly employed for many years in connection with bicycles so as to allow the users of such bicycles to vary the particular mechanical advantage associated with the operation of these bicycles. Frequently this is expressed by indicating that a derailleur mechanism provides the user of a bicycle with a selection of different gear-ratios sufficient to facilitate the use of the bicycle. It is rather common to describe any bicycle provided with a derailleur mechanism for a purpose as indicated as a xe2x80x9cderailleurxe2x80x9d even though the bicycle itself will normally utilize two different derailleur mechanismsxe2x80x94one in association with the pedals of the bicycle and the other in association with the rear wheel of the bicycle.
The various prior derailleur mechanisms used in connection with bicycles have been constructed a number of different ways. Many of such mechanisms, have utilized two different, separate controls, one of which is associated with one of the derailleur mechanisms and the other of which is associated with the other of such mechanisms. When used, these two separate different mechanisms had to be manipulated in synchronism with one another so as to avoid any possible interference with the operation of the bicycle. A recognition of the problems associated with this had lead to the development of gear shift mechanisms in which two separate derailleur mechanisms or structures are concurrently operated through the use of a single control cable. This use of such a single control cable is highly desirable in that it effectively eliminates the need for coordination in shifting a derailleur type bicycle as was required with prior common place structures having two different controls for separately manipulating the two different shifter mechanisms on a bicycle.
In spite of the obvious advantages of derailleurs employing a single manipulative control as discussed in the preceding, it is believed that there is a need for improvement in the field of derailleur mechanisms and more specifically in the field of derailleur type bicycles equipped with several such mechanisms. Specifically it is considered that there has been a continuing need for derailleur mechanisms that are more economical than prior type derailleur mechanisms. Uniquely, if the derailleur mechanisms have fewer parts there would be great cost and natural resources savings. The reduced part count can result in an increased reliability because there are fewer parts to fail and compliant members are less sensitive to contaminates, such as dirt, than are pin joints. It may also result in a reduced component weight.
Examples of patents related to the present invention are as follows, and each patent is herein incorporated by reference for the supporting teachings:
U.S. Pat. No. 4,824,420, is a rear derailleur for bicycle gears.
U.S. Pat. No. 4,887,482, is a cable-guide element for the rear derailleur of a bicycle.
U.S. Pat. No. 4,878,395, is a device for operating the gear change of a bicycle.
U.S. Pat. No. 4,106,356, is a derailleur for a bicycle.
U.S. Pat. No. 5,836,844, is a rear derailleur for a bicycle.
U.S. Pat. No. 4,637,809, is a rear derailleur for a bicycle.
The primary objective of the present invention is to provide a derailleur, and more particularly, a bicycle derailleur device that is compliant and self returning.
There are possible advantages of the compliant derailleur over traditional derailleurs in addition to the cost savings mentioned. This includes a possible increased reliability due to fewer components to fail, fewer parts to have tolerance or assembly problems, and they are much less sensitive to contaminates, such as dirt. A reduction in weight may also be possible because of the decrease in the number of parts.
In accordance with one aspect of the invention, there is a derailleur for moving a chain from one location to another while maintaining parallel alignment to a set of gears mounted to a cycle. Specifically, the derailleur has a first and second rigid segment, parallel to each other, where the first segment is fixed to the cycle and the second segment is free to traverse from a first to a second position. In addition there is a first linking means, coupled between the first and second segments, for linking the first and second rigid segments together, and designed to move from the first position to the second position. Moreover, there is a second linking means, coupled between the first and second segments and spaced from the first linking means in about a parallel position, for linking the first and second rigid segments together, and designed for resiliently biasing the derailleur into the first position and for resiliently bending into the second position.
Wherein the invention further comprises a derailleur that has the first linking means being shorter than the second linking means. Additionally, there is a chain wheel, coupled to the second segment, having a first axis that remains about parallel through all successive locations between the first and second positions. Moreover, there is an attachment means for attaching the derailleur to a frame. Additionally, there is a chain, coupled about a portion of the chain wheel. Uniquely, the first link is rotatably coupled to the first and second rigid segments through a first and second pivot pin respectively. Wherein the first link fully comprises a flexible material allowing the entire first link to bend into a shape approximating an xe2x80x9cSxe2x80x9d shape during movement between the first and second positions.